DISK ARRAYS

A disk array is a matrix of independent but interconnected physical disk storage units.  For the Teradata RDBMS, the disks are organized as a Redundant Array of Independent Disks (RAID), as RAID1 (mirroring) or RAID5 or RAIDS (parity) technology using RAID Manager.

Each array typically consists of from one to four ranks of disks, with up to five disks per rank.

RAID Manager uses drive groups.  A drive group is a set of drives that have been configured into one or more logical units (LUNs).  All the disks in a drive group must be of the same RAID level (1, 5 or S).

A LUN is a portion of every drive in a drive group.  These portions are configured to represent a single UNIX disk. Each LUN is uniquely identified and sliced into one or more UNIX slices.

A pdisk is a slice of LUN that is assigned to an AMP.  Each pdisk is uniquely identified and independently addressable.

The group of pdisks assigned to an AMP are collectively identified as a vdisk.  Vdisks are used to control the assignment of pdisks to AMPs.